My cat's ear bite has a foul odor. What should I do before the vet?

Owie, it looks like your kitty has a cat bite abscess in her ear. Almost all cat bites are infected, so this is not unusual. The location is rather unusual.
Maggots are gross, however in this case I think they helped clean the wound. Maggots are often used in human medicine to clean out infected wounds, so this is a tried and tested method, albeit, in your kitty's case not originally intended. This is all you can do for tonight. You did na nice job cleaning the wound and I see it is quite swollen, so now the swelling needs to go down. That might take a few days. Your vet will likely prescribe an antibiotic to keep the wound from festering again. If you have an e-collar at home, you could put that on your kitty to keep her from scratching the wound, however I suspect she will leave the wound alone anyway.